High-frequency apparatus



AUS-'27,1946 w. w.HANsEN E-rAL I 2,406,372 HIGHy FREQUENCY 'A 1=P.I\RATU-:

Filed May 17, 1 941 3 sheets-sheet v1 INVENTOR WILLIAM W. HANSEN M JOHNR. WOODYARD 5 Sheets-Sheet 2 INVENTOR WILLIAM W HANSEN dw( JOHN R.WOODYARD w. w. HANSEN ETAL HIGH FREQUENCY APPARATUS File@ My 17, 1941Aug. l27', 1946.

FIG. 6

F ll-r 7 AugQ 27, 1946.

HIGH FREQUENCY APPARATUS Y A Filed May 17', 41 94 fs Shee's-sheet s AINVENTORS WILLIAM W. HANSEN Y JQHN FLWOODYARD l THEIR ATTQN'Y.'

Patented Aug. 27, 1946 HIGH-FREQUEN CY APPARATUS William W. Hansen an dJohn R. Woodyard, Garden City, N. Y., assignors to Sperry GyroscopeCompany, Inc., of New York Brooklyn, N. Y., a corporation ApplicationMay17, 1941, .Serial No. 393,868

(Cl. 17E-44) 24 Claims.

This invention relates, generally, to the art of high frequency energytransmission and apparatus related thereto, and has reference moreparticularly, -to novel improvements in` impedance matching andtransforming devices adapted for use with this type of apparatusoperating at ultra-high frequencies, of the order of 109 cycles persecond.

In transforming energy from one high frequency device to another, it isWell known that the Value of the impedances of the respective devicesmust be properly matched in order to avoid the production of standingwaves with attendant increase in losses and decrease in the energytransmitting capacity of the system. Further, for maximum eillciency, itis known that the impedance of a load or utilization device must beproperly transformed to match that of the source.

The present invention is principally directed toward the provision ofimproved impedance matching and transforming devices which are adaptedto eflicien-tly couple and match the impedance values of the circuitelements interconnected thereby with a minimum of adjustment and amaximum of facility and efliciency.

In another of its aspects, the present invention is directed .toward aprovision of a novel sliding joint utilizable in connection with theabove-mentioned impedance matching and transforming devices, or, whichmay be employed generally in ultra-high-frequency coupling arrangementswherever adjustability and` smoothness of transition are desired.

A principal object of the present invention is to provide novelimpedance matching means for matching the impedance of an apparatus ofthe above character to that of other apparatus, such impedance matchingmeans being designed for versatile operation in that it may efcientlyconnect two impedance elements havingimpedances of different values withhigh elciency of power ilow therebetween. Y i l A further object is toprovied novel impedance matching means which is so designed as toefciently match both the resistive and reactive components of any twoimpedance elements having generally different impedance values.

Another object is to provide novel and eilicient sliding joints fortelescoping concentric transmission lines, whereby reflections andstanding waves are prevented.

A still further object is to provide a novel transmission line sectionhaving a cylindrical outer conductor and an eccentrically and adjustablypositioned inner conductor.

Other objects and advantages will become apparent from the specificationtaken in connection with the accompanying drawings, wherein,

Fig. 1 is a view in side elevation and partly in section of an electrondischarge tube structure adapted to be used in a high frequencytransmitting and/ or receiving system wherein the present invention mayadvantageously be included. y"An electron discharge tube of theindicated type is disclosed and claimed in acopending divisionalapplication filed in the names of the present inventors and bearingSerial N o. 420,771;

Fig. 2 lis a perspective view rof the fine tuning adjustment of the tubeof Fig. 1;

Fig. 3 is a longitudinal sectional view of one typ of impedance matchingdevice, or impedance transformer;

Fig. 4 shows a radio transmitting system incorporating the tube of Fig.1 and the impedance transformer of Fig. 3;

Y Fig. 5 is a view partly in section of a detail of Fig. 4;

Fig. 6 is a sectional View. of the antenna and reflector of Fig. 4;

Fig. 7 is a longitudinal section vof an alternative type of impedancetransformer;

Figs. 8, 9 and 10 are cross-sections of Fig. 7 taken along lines 8 8, 99 and Ill-I0 respectively;

Fig. 11 is a diagram explanatory of the operation of the device of Fig.7; and

Fig. 12 is a longitudinal cross-section of a further modification ofimpedance matching transformer.

In the drawings, Fig. 1 shows an electron discharge tube structure Icomprising an indirectly heated cathode 2 having a heater 3, amodulating grid 5 and spaced, cylindrical, resonators or resonatingchambers'l, 9, II. These resonators have rigid dished walls I3, I5, I1and opposed ilexible walls I9, 2|, 23, respectively, the dished wallsbeing centrally apertured and provided with grids. 'Flexible walls' I9and 2l of resonators 'l and 9 are joined by a' drift tube 25 also havinggrids at it-s ends opposite the grids of Walls I3 and I5. This tube 25has a central threaded portion 21 for retaining'a thrust plate 29thereon. The main body 33 of the tube I carries a flange 35 which hasseveral threaded holes 3l, in this case shown, for illustrative purposesonly, as three in number although only two are visible in the showing ofFig. 1. These threadedholes 3l carry thrust screws 39, one end of eachof which terminates in a shape suitable for the application of a Wrenchfor turning the screw, or in a'slot for receiving a screw driver, whilethe otherL end terminates in a socket adapted to receive the ball headsVof .thrust rods 4l, 43. The screws 39 also have lock nuts formaintaining them in their set position. TheV other end of each of thethrust rods 43 is placed'in a socket in the thrust plate 29 similartothe sockets in screws 39. The plate 29 has rigidly fastened to it, asby screws 41a resilient cantilever leaf member 49. The

member 43 is fastened to plate 29 YatQone end only, in cantileverfashion. The unfastened end of cantilever 9 is adapted to be moved bythe movable stem l Vof a tion of handle 51 results in transmission ofthrustv to cantilever s through ball 59, resulting in deflection of theresilient cantilever; 59. Thrust rod- 4| is socketed at one the fastenedend of this member,l and Yat the other end in its screw 39.

Fig. 2 shows plate 2Q with rodst and/Sdn their normal operatingposition. These rodsv are, held in position in the actual device by theopposition to deformation of the rresonating chamber 'l' created largelyby atmospheric pressureacting on the evacuated casing 3%; as describedbelow.

HWhile the cantilever tuning'v means has been ries a tube l l4terminatinginiouter coolingfns 13.,

Mounted on this tube 'HV is another thrust plate l5 carrying thrustscrews 'Fll bea-ring against thrust rods 'iS which in turn bear'againstiiange 63, the usual lock nuts 8| beingprovided.

Eachy of theresonating chambers l, 9, l-lI has provided means for,supplying or abstractinghigh frequency energy in the form of concentricline terminal posts whose inner conductorsterminate in coupling orpick-up loops 815.

end in the member mearmicrometer arrangement. 53 mounted as by bracket55 on plate 29. Rota-l In operation, electrons emitted by the cathode 2forma beam which `may be modulated bysupaplying suitable potentialstogrid''.; The electrons are accelerated by the potentialIdiierenceibetween cathode 2, usually maintained; at a high negativepotential, and'rigid" wall I3; which acts as an accelerating electrodeand is `usually grounded; As is well known, thepassing ofthe beam.throughA the rst resonating chamber T, knownA as the buncher effectsrecurrentchanges invelocity ofthe electrons, ofthe beam. Passage ofelectronsthrough the drift tube 25 permits the electronsto'bunch, and togive up their energy upon passage through the secondresonator 9, knownas the catcheri Output energy cannbe obtained from the resonator 9.However, morder to prevent theabstraction of energy from affecting thefrequency characteristics ofresonator il andof resonator l, which may,in someY applications of the device, be coupled to resonator',v theelectron beam, now bunched, is allowed to pass through the furtherresonator I l, and output energy is` obtained.from Vthis resonator,whichlcannot reflect back into4 the other resonators 'i and 9 Y tochange their frequency characteristics since it' is coupled tothe otherresonators only by the electronbeam. The novel tube of this inventionthereby includes a buffer. stage or resonator, as well as the buncherand catcher stages or resonators.

.Asis well known, the frequency of operation of such devices as thepresent depends onthesize and shape of the resonating chambers; Thepresent invention providesl means for'adjustingv the frequencyof-each-of the/resonators. Thus, it is cleary that turning screws 'Hwill create a-thrust between plate l5 and ilange E3, kwhich Willbetained by this means.

` chamber, which tends to collapse the flexible wall. This adjustment ofscrews 'Il' therefore causes deformation of the flexible wall 23,thereby changing the resonating frequency of this resonating chamberOnce adjusted, the frequency may bemaintained by use of the lock nuts Elto maintain screws 11 in desired position.

Turning screwsY 55 will in like manner create relative thrust betweenthe rigid and flexible walls of resonator 9 and causetuning of thisresonator. It will be noted that this tuning cannot affect the tuning ofresonator l-I, since no between the rigid andA flexible walls `ofthatnresonator by turning screws G5. At most, a slight motion oftheWholeresonator H occurs,- due to deformation of flexible Wall 2|v ofresonator Si InV the-same manner, the frequency 0f resonator 'lcanf-bevadjustedby screws 39; Here again', no effect is produced oneither of the otherlresonators. Itis obviousthat the tuningof-each-'ofthe resonators isindependent of anyl other,- andthe resonatorsmay beadjusted in anyY desired order;

In the case/of resonator 'I there-is further provided the novel necantileveradjustment for tuning above described.V y It willbe seen-thatturning micrometer handle 51 will createlathrust on resilient cantileveriii through ball' 5e: This thrust is transmitted'to rod il bythecantilever actiony of member-:159- and thence toresonator chamber l.A dual refinement of tuning-isch'- First, there is `the reiine-l ment byuse of a micrometer screw insteadofthe ordinary screws Se. Thereis asecondgreflnee ment in tuning by use'of the cantilever arrangement, evenover an ordinary rigidA lever, arrangement. AIf anordinary lever wereused, pivoted-at f wouldbereduced screws lil', the/motion of rod 4Irelative to that of micrometer rod' tby aI factor which is proportionalto the ratioof their relative distances from the pivot. The novel methodhere used-obtains a further reiinement'overl such a pivoted leverarrangement, since thereduction in Adeflectionorod 4l, using the`cantileveriar'- rangementv and` neglecting the` opposing; force createdby rod El, isby ar factorroughly'proportionalvto thev square of theratio of the' relative distances, sincethe cantilevenassumesa roughlyparabolic-shape. Furthermore, the effect'ot'the opposition'of rod i tobeing moved bythe application of force to the endof 'the; cantilevertg'is to further reduce'therelative motion, van'dtoeffe'ct furtherrefinement`4 of tuning. point of View, thisl results in-furthercurvature of the cantilever spring, makingjfthe deilectionv of rodilproportional to .the appliedlmotionby a factor which is inverselyproportional to .even higher powers ofthe distance ratio than thesecondpower; It-willbe seen thusV that extremely ne andv sensitive tuningadjustments can. be made, which is essential forv successful operation,

especially in small tubes operating'athighfrethrust is` created .Fromanother The transformer 81 is illustrated as comprising a central sleeve9| in which are mounted the ends of spaced concentric transmission lines93, 95 Whose outer conductors are permanently connected to sleeve 9| andwhose inner conductors extend radially inwardly of this sleeve 9|. Theselines may be open stub lines or terminal posts having their remote endsadapted for connection to other transmission lines or loads. .Twocylindrical end members 91, 99 are carried by or formed in sleeve 9 I.The members 91, 99 are bored to a suitable diameter for receiving aslidable snorting plug carrying a reduced rod |03. The size of the borein member 99 and the diameter of rod I 03 are suitably chosen to form aneicent concentric transmission line. The remote end of rod |03, shownreduced, is threaded as at |05. Upon this threaded portion is screwedsnorting plug |01, which ts snugly but slidably in the bore of member 91and has an enlarged portion |09 serving as a knobwhereby the distancebetween the inner faces of plugs |0| and |01 may be varied by turningknob |09, and the entire unit composed of plugs |0I and |01 and rod |03may be slid back and forth longitudinally within outer members 91, 99and sleeve 9|, by longitudinal translational motion of knob |09.

Rod |03 slides within a fixed sleeve I I, whose outer diameter is soselected that it bears the same ratio to the inner diameter of sleeve 9|as the diameter of rod |03 does to the bore of members 91, 99. Sleeve I|I is permanently connected to the inner conductorsof transmission lines93, 95 and is therefore immobile with respect to sleeve 9| and members91, 99. Sleeve |II tapers down to the size of rod |03 at its endproportions, as shown. Members 91, 99 have a corresponding internaltaper. These tapers are s0 chosen as to maintain constant the ratio ofthe sizes of outer diameter of the inner conductor to that of the innerdiameter of the outer conductor, thereby preserving substantiallyconstant characteristic impedance for all sections of this concentricline element. l

The method of operation is as follows: knob |09 is turned until thedistance between the inner faces oi shorting plugs |0| and |01 isapproximately one-half wave length atthe operating frequency. rlhen thewhole inner portion, comprising rod |03 and plugs IOI and |01, is slidback and forth until the proper match is obtained. At the optimum point,the device connected to line 93 in parallel with the short circuitedstub line to the left 0f the connecting point of line 93 is matched,over the section of line between the connecting point of 93 and that of95, to the device connected to line 95 in parallel with the shortcircuited stub line to the right of the connecintg point of 95.

The impedance transformer of Fig. 3 will match, with certainlimitations, a device o-f any impedance value to another device of anyimpedance value connected therethrough. It lis perfectly symmetrical inaction; that is, when a lower impedance Value is to be matched to ahigher impedance value, the device having either one may be connected toeither terminal of the impedance transformer.

Fig. 4 shows an arrangement using the above impedance transformer inwhich resonator 9 is coupled back to resonator 1, as by transmissionline I I2, thereby causing tube to generate oscillations. The output oftube I is taken from buffer resonator I I by means of transmission lineII3 to preserve stability of oscillation, and is connected,

by means of phase adjuster I 1, impedance trans'- former 81andtransmission line |I5, to a load shown as antenna 89. This figure showsan electron discharge tube of the type described above, coupled to anantenna 89 by means of transmission lines II3 and II5, phase adjuster|I1 and impedance transformer 81. In tube I, resonator 9 is showncoupled back to resonator 1 by line I I 2, to provide oscillations.Transformer 81 and phase adjuster` 1, which is of the sliding joint typefurther described below, are shown as mounted on a base I I9 by means ofbracket I 2| which holds the impedance transformer 81 and the xed part93 of the phase adjuster II1. The movable part ||4 of the phase adjusterI|1 is connected to screw |23 by a member |25. The screw |23 is threadedinto the bracket |2| so that rotation of the screw 23 will producerelative motion between the two parts of the phase adjuster I I1.Transmission line I I3 is connected directly tothe buffer stage outputof tube I `and is connected to the input of impedance`transformer 81 bymeans of the sliding joint of phase adjuster |I1 more fully described inconnection with Fig. 5. As an illustrative example, let us take theoutput impedance of the tube I to be 30 ohms. Then, transmission lineI|3 may be modified by the variable section of phase adjuster |I1 to' bea, half-wave (or multiple of a half-wave) line, so that thek impedanceat the input of the transformer, looking back at the tube, will also be30 ohms. The transformer is then adjusted to transform this value ofimpedance to some value such .as '72 ohms,jand then a 'Z2-ohm line (i.e. line I I5)L is connected to the output of the transformer. This'l2-ohm line I I5 is then shown connected to a :S6-ohm quarterwaveantenna 89 by means of a matching section |33 shown more in detail inFig.

The sliding joint phase adjuster of Fig. 5 has a lixed part 93, withinner conductor I 3 I, and a sliding part I I4, with inner conductor|29, and relatively movable by means of screw |23. With the ordinarytype of sliding joint it is almost impossible to avoid Iwave reflectionbecause of the discontinuities involved. The joint of Fig. 5 is designedto avoid these reflections. The inner conductor |29, which slides overthe inner conductor I3I, is extended one-quarter wave length beyond itsouter conductor II4. Furthermore, the relative dimensions of conductors|29 and 93 are so chosen,

that the section of line between points P and Q has a characteristicimpedance which is the geometric mean of the impedances of each-of lines93 and II4. Methods for calculating the dimensions of transmission linesto obtaina given impedance are taught in standard textbooks, such asRadio Engineering, by F. E. Terman (2d edition, p. 698). In this Way,the extended portion of conductor |29 forms with the outer conductor 93a quarter-wave matching line which causes lines 93 and II4 to be matchedperfectly without reflections occuring.

Fig. 6 shows a tapered line section |33 for matching the line II5 to thequarter-wave antenna 89. In the example used above, this line section|33 would have to match the 'l2-ohm line II5 to the 36-ohm antenna 89.This section |33 is one-half wave length long, and has an exponentialvariation of impedance with length. Thereforagthe diameter of theinnerconductor varies as an exponential function of an exponential functionof the distance along the line` section.

The variation of inner-diameter shown in Fig. 6 is that needed formatching in the illustrative anode-7.a

example .useda For matching -othervalue'soiixnpedancethe prole of theinner conductor! may bef-concave', instead of `convert as shown', or'mayheb-oth` concave and convex With a poi-etici in-r fiection, dependingion theparticulair valuesof impedanceto be matched.

'The' explanation of the-l operation of thisnline section to. prevent"reflections andstanding waves is'similar'to that'v of. the usual quarterWave line section. InI such a: quarter wavesectiom a trave elingl Wavewill seti un a reilection at the' beginningv of the-section.Theunreflected portion will travel quarter-Wave length furtherr and set`up a second reected vvaveat thev discontinuity at the section. Thisksecond. reflected'vlave Y' the end of W-ill travel back quarter-wavelengthand Will then be out' of' phase with hence thev two reilect'edwaves* will` neutralize', provided4 the proper amplitude relationsare:ob served.' This is insured by having the character-- isticimpedance'of the. quarter-Wave length section equal the geometricme'an'of the two in1- pedances to be matched.

The present half-Wave length sectionv operates in a similarmanner; thatis, the reflectedwave at'the end |23 ofthehalf-Wave length section|33is' used to neutralize the Wave setup. ati the beginning |39 of thesection 33. One important difference exists here: in the case ofy theordinary quarterwave lengtliisection, the change in impedance at'the'vpoints of discontinuity is in the same directionl at both'. en'dg of'the line section; that is", both-have increasing impedance values orbotnfhave decreasing impedance values. In the case of'the presentsection. 33, the types of discontinuity are opposite; that is, thereisabreak' from constant" impedance to: varying im the'r rstreiie'cted Waveand pedance at mi, and then a' sec'ondlbreak' from varying impedance toconstant impedance at |28. This introduces an additional?.v 180degrees'phase shift between the two reflected Waves. Hence, forneutralization, the line must be half-Wave length (or 180 electricaldegrees) long, softhat adding up the phase shifts caused by the" directwavetravel time, the reiiection, and the reflected Wave travel rtimewill result inzphase' opposition; The proper amplitude' relations" areobservedby having an exponential variation ofim'- pedancealong'thesection |33. Since impedance variesfasth'elogarithm of the ratioofioiuter"con-V ductor diameter to' inner conductor diameter, and sincethe outer conductor |331 is constant` inrdiameter, this necessitates adoublyu exponential Variation of the diametericftheinner conductorV|3121' v Figs. 7- to 10 show an alternativeforrn of i1npedanceltransformer'Whichwilloperate to transforxn or matchf theimpedance of a fixed impe'.- dance element into anydesired impedancevalue. It mayi serve' to match a device' having an'arbitrary impedancevalue with that of a particular concentric transmission: line. Thismatching transformer' has an` inner conductoriSS which has anintermediate. onset portion i3?` at'. least three-quartersci a Wavelength long. Fixed to the. inner conductorv |35. are two sleeveportions|39,. |4| xedly joined to theinner conductor byinsulati'ngimember's |43.Slidably, mounted-Within sleeve |39 and outside of conductor |351 is vaconducting sleeve i'rnaintained elec trically'separate from conductor|35l byinsulating member HW.'Y Theinsulating member |51 slides onconductor |35 and is iiXed to sleeve I. Obviously, member IM couldijusta's-vvellbefxed to? conductor |35 andi sliderv invsleeve-Iv 45. Y-A-sleeve pacitanceand.'therefore to |49? isi similarly arrange'd.'Within sleeve,` MI.f Sleeves |45fand. i'fhave thin-Walled sectionsf|514 and will extending away.' frorn the center of: the device: These?thinewalled, sections are exactly onequarter'wave length long andsodimensioned that. anale-gunste: thedevice of Fig;r 5, the thinwalledsections' act as quarter-Wave matching 1ines=between=the terminallineand the line cornposedof sleeve Ilia (or SL19) and conductor' |35,the'chara'cteristic impedance of these matching line'sibeingequalto.the. geometric mean of the impedances'r of thelines immediatelyconnected thereby Each of these sleeves |45 and' HiB has a=tapered-portion |51 which may be slotted axially. FixedlyI attachedl tosleevesl-4 and m9,' are threaded.. ring-s` |5'.. Theseengagewvvithclamping rings' `l 552 havinga taperedk portion mat'- ing'` with taperedportion 52', I-`whereby, upon threading-clamping ring len ring l;the-taperedportion.. l5 if isi' clamped against sleeve M5 or M9,servingct'o keep rings Saandv M5, orgie-i and M9, in theiryadjustedpositio'ns. SleevesA M25 and |49 are joined, by an eccentricyokev mernber |511 Sleeves lll'andjlmay have flanged ends'asfat m91 Yoke|5iisprovid'ed WiththreadM edV portions ll cooperate withfrings it toprevent-sleeves |655k andi |69 fromany relative axialmotiomWhile'leaving. yoke ilfree tor tate.Y rIhe'por-tio'n of yokeli'which-cooperates with offset portion. |31 orV the inner conductor isexactlyfonequarterfWave length long.

Inner conductor.'A |35' and Isleeve |39 (or ISH) may have' any relative:sizes', but arefpreferably so proportioned as tof constitute one of-theusual concentric transmission line sizes.V The portion of the;transmission; line: formed by the offset inner conductor i3? and sleeve|45 (or |59) is proportioned t'o--lo'zwathe same impedance asthe Y,

porti-on of lin'e'.- constituted` by.- innerconductor |35 and outerconductor ist: (or Ml), so that no losses or.' reflections.. Will beencountered at the junctions of offset andregular portions; effectoioffsettingfthe inner conductor of a concentric transmission line is toincrease its cadecrease its character-v istie impedance' TheY effect ofdecreasing. the diameter ofthe inner conductor oi" a concentrictransmissionline is to increase its characteristic impedance'l Hence',the diameterr of the offset portion' ofthelinner conductor is reducedbythe amount necessary; to compensate for the decreasedcharacteristicimpedance caused by oil- Y setting,V leavingithenet impedance the same.

The diameter of theeccentric openingin yoke |51r is adjusted so thatatthe most eccentric position of". the rotation of yoke E, the yoke justtouchesthe offset' innerf conductor I3?, as shown in Fig.` 9,' and at`theV other extrerneof rotation the inner conductor |31 isconcentricWith-thc sleeve opening, asshovvnl in Fig. 8. Forother'deg-rees` ofA rotation there will be spacings' of inner 'conductorl'with respect toy yo-ke'ril varyingY l front-thatrshown in'Fig.y 9 tothat shown in Fig. S.

Endcaps andV adapters |65 for connectingv the device 'toi standardlconcentric transmissionlines are.' provided, usingl the proportionaltaper explained; in connection with Fig. 3.

The operation of the device of Fig: 7 can best be explained'on the basisofthe diagramof Fig. 11; Thisilguren shows', on animpedance-diagraniWhoseI coordinate aXes represent resistance and reactan, theconstant-coordinate lines of aibipolar coordinating system'having polessuch asfZo.v Onlyf the right half of this diagram is shown, the left.half. beinga mirror image oflthe The 9 right. 'Ihese constant-coordinatelines form two families of circles, one family with centers on theX-axis (axis of reactance) and passing through both poles and the otherfamily having centers on the R-axis (axis of resistance) such that eachcircle of one family crosses every circle of the other family at rightangles. This system, therefore, forms an orthogonal curvilinearcoordinate system known as the bipolarcoordinate system. It can be shownthat, if the poles of such a system are chosen to be th'e pointsrepresenting the characteristic impedance of a transmission line, and ifan arbitrary impedance value is selected, such as represented by point Zon Fig. 11, and connected to varying lengths of the transmission line,`then the net impedance, looking from the remote end of the transmissionline to impedance Z, is represented by points moving along theconstant-coordinate circle ZRiRz passing through Z. This impedance locusmakes one complete rotation around Zu, back to Z, for each halfwave-length of line added. Thus we see that, in order to tune impedanceZ to resonance, enough line must be added to carry the net impedance topoint R1. This would give a high resistance resonance condition. If moreline is added, we finally reach a low resistance resonance point R2.

The above theory is used in the operation of the device of Fig. 7. Letus assume, for illustrative purposes, that sleeve |39 and conductor |35make up a '12 ohm line. It is desired to match a '12 ohm line to anyarbitrary value of impedance, not necessarily purely resistive.Y The 72ohm line is connected to the left end of the impedance transformer,which it matches since it has been assumed that this left endconstitutes a 72 ohm line. The element having any arbitrary impedancevalue is connected to the right end of the device. The length oftransmission line between the element of arbitrary impedance and thebeginning of eccentric sleeve |51 is then adjusted by sliding sleeve |49within sleeve |4| until the value of arbitrary impedance plus that ofthe line, looked at from the beginning of the eccentric sleeve |51,exhibits minimum resistive impedance. This corresponds to transformingthe point Z (Fig. 1l) to point R2 by adding a length of linecorresponding to th'e heavy arc ZRiRz. If we look to the left from theleft edge of the eccentric-sleeve |51, there is also exhibited a pureresistance, since everything connected to the left end of thetransformer is matched. This resistance however, is not R2 but Zu.There-remains the step of matching two purely resistive impedances ofdiiferent values. 'I'h'is is done by rotating the eccentric sleeve |51to the proper position, which will be that at which the quarter wavelength line |51 exhibits a resistive impedance R3 equals \/Rz.Zo, i. e.,the geo-metric mean of the two impedances to be matched.

Since the sleeve |51 constitutes a quarterwave length line, itsimpedance will always be resistive. Rotating the sleeve will vary theposition of the inner conductor |31 relative to the outer conductor(sleeve |51) from that shown in Fig. 8, which has maximum resistance, tothat shown in Fig. 9, which has Zero resistance. If the eccentricsleeve'cpening is properly proportioned relative to the diameter ofoffset inner conductor |31, the quarter wave length line can exhibit anyresistance from Zero to a value at least as large as Zo, so that byproperly positioning the sleeve, the required-resistance, such as l0 R3(Fig. 11) can easily be obtained, providing substantially perfectmatching.

Fig. 12 shows another embodiment of impedance transformer which also canmatch .the impedance of any impedance element to th'at of any otherimpedance element. This embodiment comprises a concentric line devicehaving an outer cylindrical conductor |91 in which is fastened aperpendicular sleeve section |69 of equal diameter. Supported withinconductor |51 as by insulator |1| is a concentric inner conductor |13which also has a perpendicular section |15 of equal size which isconcentric with section |59. A reducing end cap having tapered portion|11 similar to |95 in Fig. '1 is provided for coupling this device to astandard line or other impedance. The diameter of the concentric linesection forming the impedance transformer is made larger than the lineto which it may be coupled'in order to increase eiiiciency of operation.y

Sliding within sleeve |99 is a movable snorting disc or plunger |19moved by plunger rod 8|. The snorting disc |19 carries spring fingersY|83 which make good electrical contact with conductors |69 and |15 whilepermitting sliding motion. Sliding within sleeve |51 is sleeve |85.Fastened concentrically within sleeve |85, as by insulator |81, issleeve |89 which has an inner diameter chosen to give sliding contactwith rod |13. An end cap and tapered section |11 is also provided forthis end of the device.

Inner sleeve |89 ends one quarter of a wave length within the end ofsleeve |85. The portion of sleeve |85 not opposite sleeve |89 (that is,the last quarter wave length) has a thickened wall, formed in thisinstance by inserting sleeve |9| permanently fastened to sleeve |85. Thedimensions of conductors |91, |13, I 9|, |85 and |89 are so ch'osen`that the characteristic impedance of the Lili- |13 section of line isequal to the geometric mean of the vcharacteristic impedances of the|51-|13 and |85| 89 sections, thereby avoidingreflectionsvat the slidingjoint, as discussed above.

Accordingly, an impedance matching transformer has thus of arbitraryimpedance values may be matched by adjustment of the length of a sectionof concentric transmission line connected in cascade with one of thearbitrary impedance values and by the subsequent adjustment of thelength of a short-circuited section of concentric transmission lineconnected in parallel with the cascadeconnected transmission linesection.l It is understood that the order of these adjustments isimmaterial. f

The theory and method of operation of the V'device of Fig. 12 may beexplained on the basis of a diagram similar to Fig. 1l, but wherein thecoordinate axes represent susceptance B and conductance G rather thanreactance X and resistance R so that the diagram represents admittance Yrather than impedance Z. Such an ad-v mittance diagram coordinate systempoles would be the would have the same bipolar as shown in Fig. 11,butthe characteristic admittance instead of characteristic impedanceZo.VFor simplicity, Fig. 11 will be used again, it being understood that,wherever the symbol Y is used, the

admittance diagram is meant.

Now, if it is desired to match two loads having admittances Y1 and Y2,respectively, it will be been provided whereby any` pair' Such addedsusceptance is Yferent embodiments of i121 necessary .to match :bothfthe fsuscentanccs and conductances of these'loads. YBySgrafdually sadd-V ing transmission sline .having .admittance sin to 4Vsusceptance, wecan match uthe :admittances 'iYl and and therefore theimpedances,perfectly. obtained by .varying thelengthiof Vstubline .I 69.-.- I15,'-by1moving plunger :|81 in Ior out to .add :the proper amount ofsusceptance v.in 4parallel lwith the line .section 'ljBL-Jll'l-S. lftheadmittance Ya-shouldhetvholly to l:the right or left of the circletraveled byYi,

thentit is merely necessary to interchangeYl and Y2; .that is, Y2 wouldthen be connected to the tightend ofithedevice vof Fig. =12.

'From the above analysis, itis evident that to `use' the 4deviceo'fllig. 12, 'itis:merelyinecessaryto connect Loneirnpeda'nce `elementkat Teach then vary-.thelength of line at the sliding lio-int :until the.conductancesbecome matchedgand thenvary the `Ashorlting lplug =untilthe -susceptances .are matched. Then the impedance values/of the twoimpedance .elements will 'be matched.

As .many rchanges could be'fmade in v`the above constructions :and manyapparently widely ldifthis invention `:could be made without departingfrom :the scope thereof, it `is intended Ythat all matter `conta-ined inthe above `description orshown -in the accompanying drawings shall l-beinterpreted as illustrative and not in a 'limitingsense "What'is claimedis:

1. A transformer device for matching `the admittances of any two`circuit elementscorn-aris-V ing adjustable `meansfor converting theconductancefof `one'of `said elements to a rvalue equal '-to that `of:said other element, land independent Aadjustable Arneansffor addingsubstantially pure susceptance 'to sa'id vconverted conductance to fullymatch said Vtwo admittances.

#2. VJ'Apparatus for matching twocircuit-elements having any admittance`Vvalues Vcomprising ja sectionof-:transmissionline o'f the-coaxialconductor type xadapted for :connection between said circuit elements,-means Alion-varying the length of said line'section for making theconductance offene cfsaidicircuit elements equal to the conductance oftheother circuit element, and ffurther means for .adding .substantially=pure suseeptance to one of fsaid :circuit elements until 'both circuityelements have fthe same values-of susceptance. Y

' 3. An impedance transformer for transformingV an arbitrary yimpedancevalue to fanotherjarbitrary yalue, comprising an adjustable 'lengthsection of concentric transmission 'line 'adapted to `be connected Aincascade to said arbitralyfimpedance value, and an adjustable 'lengthofshort circuited .section .of concentric A transmissiondine connected1in shunt `,to said first sectionintermediate the ends thereof, whereby,said .other arbitrary impedance value .may fbe .obtained `.by v

adjustment of the lengths of said two sections.

4. An impedance transformer for matching the impedances of two -circuitelements having` any impedance values, comprising an adjustable lengthsection of 'transmission line adapted to loe connected in cascadebetween.said elements, fand an adjustable length section of .transmission lin-econnected .in shunt Atosaid .rst,s ectdon intermediate the ends thereof,whereby saidl impedanccs may7 be Amatched-.ley adjustment of the4lengths of said twosections. 1

5. rin impedance ymatching transformer com'- pnising asection of hollowtransmission line havinst la vfixed unitaryinner conductor, meanscooperating witha section of said inner conductor il.An.impedancetransformerfor matchingany y two .impedances comprisingmeans yincluding an adjustable length section .-of concentrictransmission `line connected fin .cascade with one of said limpedances.for converting the conductan ce of .said .one impedance .toga valuevequal to that of .said ,.other impedance, and ,means including anadjustable length .short-circuited section of concentric vtransmissionline `con-necteri in parallel with said rst section for addingsuscepta-nce to said .converted impedance to 'fullymatch saidVtwoimnedances. f

8. .An .impedance matching transformer comprising .a .transmission Ylinesection of the coaxial conductor .type .and of .substantially invariantover-all 'length having an l.outerYc ondilctor :made up ,of an .axiallyadjustable :central `rsection ,havinga portionof-eccentricfboreand-relativelyyfi-xed end sections for telescopingly lreceiving isaidcentral section .upon .adjustment jof said central section, .and aninner .conductor cf `iixed :length :extendingfbetweenandxed tosaidfendsections.Y

9. Apparatus for .transforming any :arbitrary impedance value .toanother vvimpedance -value comprising a -xed lengthofvcoaxial typetra-ns-` mssion -line .having input and output terminal portions and:adapted .to .be connectedsat one of said portions .toa circuitelemerrthavingsaidgarbitrialjyimnedance value, adjustable transmission linemeans .having variable characteristic impedanGe coupled ,in .Cascade.between said 'termina-l portions and .mutually zcooperable means ateachOf ...Said .terminal portions for simultaneously equally and .Qinositely.varying the length offline fromy one of said terminal'portions tovsaidvariable characteristic :impedance means and the length of Y.linefrom .the ,other of .said terminal portions to .said variable:characteristic -impedance means.

1 0. A n Aimpedance `matching transformer for matching la transmissionline to any load, -comprising means, includingV an adjustable ,sectionof transmission line having a telescopi-ng .cylindrical louter conductorand a .concentric inner conductor vwith Van off-set .eccentric portion,.for converting the impedance of said load to a Pure resistance, andfurther means, including a quarter centric :to .saidtend pieces, and a:sliding :member 1 variable impedance comprising a quarter wave sectionof conductor having a bore eccentric to and surrounding said olf-seteccentric portion and rotatably xed between a pair of outer conductorsections slidably engaging said end pieces, whereby, by translation ofsaid sliding member, the reactance of one concentric transmission line,connected to one of said end pieces and said inner conductor, may bematched to that of second concentric transmission line, connected to theother of said end pieces and said inner conductor, and by rotation ofsaid eccentric quarter wave lsection the resistances of said reactancematched line may also be matched.

12. An impedance transformer as in claim 11 wherein the diameter of saidoff-set portion of said inner conductor is reduced by the amountnecessary to match the impedance of the line formed by said concentricinner conductor and said outer conductor section to the impedance of theline formed by said eccentric inner conductor and said outer conductorsection.

13. An impedance transformer as in claim 11 further including means forpreventing reflections at said sliding joints, comprising a changedinner diameter of the inner one of said slidingly engaged conductors forla quarter wavelength from said joint, said changed diameter being ofthe proper amount to make the characteristic impedance of the linesection comprising said changed diameter of a value substantially equalto the geometric mean ofthe characteristic impedances of the neighboringsections of concentric transmission line.

14. An adjustable concentric transmission line comprising a iirstsection having an inner conductor and a concentric outer conductor, asecond section having ,an outer conductor adapted to slidingly engagethe outer conductor of said iirst section, and having an inner conductoradapted to slidingly engage the inner conductor of said iirst section,one ofV said conductors of said second section extending a Vdistanceequal to a multiple including unityof a quarter of a `wave length of theoperating frequency beyond the other of said conductors of said secondsection, whereby a portion of said line is formed by one conductor fromeach of said sections, the dimensions of said inner and outer conductorsbeing so chosen that the characteristic impedance of said portion has avalue equal to the geometric mean of the characteristic impedances ofsaid two sections.

15. The transmission line dened in claim 14, wherein the inner conductorof said second section extends said distance beyond the outer conductorof said second Sectio 16. An adjustable concentric transmission linecomprising an inner conductor, a first sleeve surrounding said innerconductor, a second sleeve surrounding said inner conductor andslidingly iitting said first sleeve, the inner diameter of the endportion of the inner of said sleeves being different from the innerdiameter of the adjacent portion of said inner sleeve for a iixeddistance of substantially one quarter wave length of the operatingfrequency, the inner diameters of said sleeves and the outerdiameter ofsaid inner conductor being so chosen that the characteristic impedanceof the section of concentric transmission line which includes said endportion has a value equal to the geometric mean of the values of thecharacteristic impedances formed by said two sleeves and said innerconductor, whereby no 'wave reflections are obtained at said slidingjoint.

17. A transmission line comprising e. hollow tubular outer conductor, arst section of inner conductor substantially concentrically mountedwithin said outer conductor, a seco-nd section of inner conductorcomprising a continuation of said first section but eccentric to saidouter conductor, and a rotatable portion of said o-uter conductor havinga bore eccentric to the remainder of said outer conductor, said borebeing disposed about said eccentric inner conductor section.

18. An impedance matching transmission line device comprising a hollowouter conductor made up of a central portion and telescoping tubesproviding end portions adjustable in length, a substantially concentricinner conductor having an intermediate section eccentric with saidouterconductor, and a rotatable section of said central portion of said outerconductor having a bore eccentric to said outer conductor and disposedabout said eccentric inner conductor portion.

19. A reflection eliminating transmission line joint comprising twosections of transmission line of the coaxial conductor type, meansinterconnecting said sections for relative axial adjustment, and meanscomprising an impedance matching section in said line between said'twosections, said matching section having a ratio of diameters of inner andouter conductors different from that of said other two sections, andsaid matching section having a xed axiallength substantially equal to amultiple including unity of a quarter of a wavelength of the operatingfrequency, which xed length is maintained 'during all positions ofrelative adjustment of said two sections.

20. A reflection eliminating transmission line joint comprising twosections of transmission line of the coaxial conductor type, meanstelescopically interconnecting the outer conductors of said sections forrelative axial adjustment, and means providing an'impedance matchingsection in said line between said two sections, and having a I ratio ofdiameters of inner and outer conductors different from that of saidother two sections, said matching section comprising the terminalportion of one conductor of one of said two sections extendedcoextensive with the corresponding other conductor of the other of saidtwo sections, and said terminal portion having a xed axial length ofone-quarter of the wavelength at operating frequency, or a multiplethereof, which fixed length is maintained during all positions ofrelative adjustment of said outer conductors.

21. The transmission line joint dened in claim 20, wherein said terminalportion is an Vextension of one'of said outer conductors.

22. The transmission line joint defined in claim 20, wherein said twosections have substantially common inner conductor means, and said terminal portion is an extension of one of said outer conductors.

23. The transmission line joint defined in claim 20, wherein the innerconductors of said two sections are slidably engaged, and said terminalportion is an extension of one of said inner conductors beyond itsassociated outer conductor.

24. The transmision line joint dei-ined in claim 20, wherein the innerconductors of said two sections are slidably engaged, and said terminalpor# tion is an extension of one o said outer conductors. WILLIAM W.HANSEN. JOHN R. WOODYARD.

